The present invention relates to application of sonic energy, such as focused ultra sound energy within the body of a living subject such a human or other mammalian subject.
Various forms of therapy can be applied within the body of a human or other mammalian subject by applying energy from outside of the subject. In hyperthermia, ultrasonic or radio frequency energy is applied from outside of the subject""s body to heat the tissues. The applied energy can be focused to a small spot within the body so as to heat the tissues at such spot to a temperature sufficient to create a desired therapeutic effect. This technique can be used to selectively destroy unwanted tissue within the body. For example, tumors or other unwanted tissues can be destroyed by applying heat to heat the tissue to a temperature sufficient to kill the tissue, commonly to about 60xc2x0 to 80xc2x0 C., without destroying adjacent normal tissues. Such a process is commonly referred to as xe2x80x9cthermal ablationxe2x80x9d. Other hyperthermia treatments include selectively heating tissues so as to selectively activate a drug or promote some other physiologic change in a selected portion of the subject""s body. Other therapies use the applied energy to destroy foreign objects or deposits within the body as, for example, in ultrasonic lithotripsy.
In most cases, the focused ultrasound energy used in said procedures is applied by an ultrasonic energy source disposed outside of the body. For example, certain embodiments taught in co-pending, commonly assigned U.S. patent application Ser. No. 09/083,414 files May 22, 1998 and in the corresponding International Application PCT/US98/10623, also filed May 22, 1998, the disclosures of which are hereby incorporated by reference herein, describe systems for applying focused ultrasound energy in conjunction with a magnetic resonance device. An external ultrasonic energy applicator is also taught for example, in FIG. 1 of Aida et al., U.S. Pat. No. 5,590,653 and in FIG. 1 of Oppelt et al., U.S. Pat. No. 5,624,382. These external ultrasonic energy sources transmit ultrasonic energy to the desired treatment location through the tissues of the body. Various proposals have been advanced for inserting ultrasonic energy sources into the body and focusing energy from such intrabody sources on the desired treatment regions. For example, FIG. 5 of the aforementioned Oppelt et al. ""382 patent illustrates a therapeutic ultrasound transducer which may be inserted into the rectum so as to direct ultrasonic energy onto the prostate gland through the wall of the rectum. Aida et al. ""653 discloses various forms of intrabody transducer arrays (FIGS. 9-12). Diederich, Transuretheral Ultrasound Array For Prostate Thermal Therapy: Initial Studies, IEEE Transactions On Ultrasonics, Ferroelectrics and Frequency Control, Vol. 43, No. 6, pp. 1011-1022 (November 1996) discloses a rod-like ultrasound transducer housed within a catheter. Such a rod-like transducer does not focus the ultrasound but instead provides a sound pressure distribution which is at a maximum adjacent the transducer and which diminishes with distance. In use, the transducer is inserted into the urethra and the catheter is cooled by a flow of water. The cooling water limits the temperature rise of the urethra wall. Prostate tissue remote from the urethra is heated by the applied energy.
Despite these and other attempts to utilize intrabody ultrasonic transducers, still further improvement would be desirable.
One aspect of the present invention provides a probe for applying sonic energy within the body of the subject. The probe according to this aspect of the invention includes a probe body having a proximal and having a distal end adapted for insertion into the body of the subject. The probe also includes a spatially distributed ultrasonic transducer disposed adjacent the distal end of the probe body. As used in this disclosure, the term xe2x80x9cspatially distributed sonic transducerxe2x80x9d refers to a sonic transducer which is capable of emitting sound from a plurality of locations spaced apart from one another. One form of a spatially distributed transducer includes a plurality of discrete transducer elements mounted at spaced apart locations. Another form of spatially distributed transducer includes a continuous sheet of transducer material. In such a continuous-sheet transducer, various regions of the sheet are spaced apart from one another and hence can emit sound at spaced apart locations. The probe according to this aspect of the invention further includes means for moving one portion of the distributed transducer relative to another portion of the distributed transducer while distal end of the probe and hence the distributed transducer is disposed within the body of the subject. Such movement changes the configuration of the distributed transducer so as to focus the sound emitted from the distributed transducer onto a focal spot at a selected location relative to the probe.
The distributed transducer may include a deformable element, which may be separate from the active elements of the transducer. Alternatively, the deformable element may be integral with a continuous transducer sheet. In the simplest embodiment, the entire distributed transducer includes only a continuous sheet element, such as an elongated strip formed from a piezoelectric material and the electrodes used to actuate those portions of the material. Alternatively, the distributed transducer may include plural separate transducer elements mounted to the deformable element at spaced-apart locations. The deformable element may incorporate an elongated beam having a fixed end mounted to the probe body and a fixed end. The means for controlling deformation may include a control element moveable mounted to the probe body. The control element desirably is a flexible cable having a distal end connected to the free end of the beam and having a proximal end extending to the proximal end of the probe body. Thus, the deformable element may be bent to the desired degree of curvature by pulling the flexible cable. Alternatively, the deformable element may include a disc like element having a central region and a peripheral region surrounding the central region. The means for controlling deformation may include means from moving the peripheral and central regions relative to one another.
In yet another alternative, the probe may include a plurality of supports movably mounted to the probe body adjacent to distal end thereof and the distributed transducer may include a plurality of transducer elements mounted to the supports. The means for moving one part of the transducer relative to the other may include means for moving one or more of the supports relative to the probe body. For example, the plurality of supports may include a plurality of elongated supports arranged generally in the manner of the radial ribs of an umbrella. Thus, the elongated supports may have central ends pivotally connected to a common member and may have peripheral ends remote from the central ends. The transducer elements are mounted to the elongated supports adjacent the peripheral ends thereof. The supports can be pivoted relative to the common member between a collapsed condition in which the peripheral ends are close to a central axis and an expanded commission in which the peripheral ends are remote from the central axis. The pivoting means may include a control member and a plurality of struts. Each strut has a first end pivotally connected to the control member and a second end connected to one of the elongated supports remote from the central end of such support. The means for pivoting the supports may include means for moving the control member and common member relative to one another. For example the probe body may include an elongated tubular element and a flexible cable may be provided in the tubular element. The cable may be attached to the control member and the distal end of the tubular element may be connected to the common member or vice versa.
In yet another arrangement, the distal end of the probe body itself may be deformable and the distributed transducer may be arranged along the distal end of the probe body so that deformation of the probe body distal end will move one part of the transducer relative to another part. For example, the probe body may be elongated and the distributed transducer may include separate transducers or portions of a continuous sheet spaced apart from one another in the lengthwise direction along the probe body. The means for deforming the distal end of the probe body may include means for bending the distal end of the probe body transverse to its lengthwise direction so as to vary the curvature of the distributed transducer. The distal end of the probe body may be advanced into an intrabody space and the probe body may be deformed while the distal end is disposed in the intrabody space. For example, the probe body may be advanced through the urethra into the urinary bladder and the distal end of the probe body may be bent while the distal end of the probe body is in the urinary bladder.
A further aspect of the present invention provides probe for applying sonic energy within the body of the subject which includes an elongated probe body having a distal end and a spatially distributed sonic transducer disposed adjacent to the distal end of the probe body. In a probe according to this aspect of the present invention, the distributed transducer is moveable between a collapsed condition in which the distributed transducer has relatively small dimensions in directions transverse to the direction of elongation of the probe body and an expanded condition in which the distributed transducer has relatively large transverse dimensions and hence extends outwardly from the probe body in one or more directions transverse to the direction of elongation of the probe body. A probe according to this aspect of the invention desirably includes means for controlling movement of the distributed transducer between the collapsed condition and the expanded condition. In a probe according to this aspect of the invention, the movement control means optionally may be adapted to vary the configuration of the distributed transducer while the transducer is in the expanded condition so as to vary the focus of sound waves emitted by the transducer.
Still further aspects of the present invention provide methods of ultrasonic treatment.